Sharif Digital Repository

This project aims to investigate environmental effect –such as dust and rain- on the performance of a vertical axis wind turbine (VAWT). However, those issues are frequently investigated in the horizontal axis wind turbines, but this subject has not been studied in vertical axis wind turbines. Impact of rain or dust particles on the turbine blades can change the turbine performance. So consideration of the impact of environmental factors on the performance of wind turbines is very important. Vertical axis wind turbines, particularly the straight bladed VAWT are widely used in wind power generation in agricultural and rural lighting and the use of this type of turbines is increasing... 

Limited fossil resources, daily increase of demand for energy and the most important one that is environmental pollution fact, make people think of renewable energy as a solution. One type of these renewable energies is offshore wind energy that has high potential without any sound and visual noises. Recently a lot of researches have carried out their studies on the topic of offshore wind turbine. Cause of disabling of a lot of software to simulating of dynamic effect of rotating rotors, so in this research has make effort to fabricate and test an offshore wind turbine with different rotor rotating velocities and different heading angle of wind, to catch the effect of these parameter on the... 

Advanced control techniques are required to achieve a cost-effective and reliable use of the wind power generation. The wind turbines are generally controlled based on two control objectives: the turbine protection and the generation of acceptable power for the utility grid. These objectives are achieved if the control inputs are applied based on appropriate control logics. In this work, a nonlinear multivariable model of the wind turbine with a DFIG generator is considered. The rotor speed and the d-axis rotor current (as the control outputs) are controlled via manipulation of the two generator voltages (as the control inputs) in low wind velocity condition. For high wind velocity, the... 

An aerodynamical model for studying asymmetric and three-dimensional flow fields about wind turbine rotors is presented. The developed algorithm combines a asymmetric and three-dimensional Navier-Stokes solver with a so-called actuator disc technique in which the loading is distributed along lines representing the blade forces. The loading is determined iteratively using a bladeelement approach and tabulated airfoil data. Computations are carried out for a 5MW NREL wind turbine equipped with three blades. The computed power production is found to be in good agreement with measurements. The computations give detailed information about basic features of wind turbine wakes, including... 

In order to reduce damage caused by power outages on rare events that lead to long-term disconnection of microgrid from utility grid, isolated mode performance of microgrids including wind and hudro turbines with energy storage systems is considered in this study. Using wind energy as a renewable resource is considered as an appropriate choice for power production in microgrids. However, the uncertainty in wind turbines power generation is something challenging. The existence of water resources near the wind farms causes a special opportunity for operation of these resources along with wind turbines. This thesis aimed at balancing energy supply and demand in island mode of microgrid,... 

The issue of solid and fluid interaction in horizontal axis wind turbines with diameter of more than 120 meters is one of the most important researching subjects of this type of turbines. This issues needs quick and exact solutions because of the high computational cost of fluid and structural domains.In this research a quick method with acceptable accuracy has been suggested which is based on computational fluid dynamic to examine the aeroelastic behavior of rotor and wind turbine tower. The actuator disc method in two domains of axisymmetric and three-dimensional has been used to compute aerodynamic forces. For this purpose a code has been written in C++ to set down virtual momentum on... 

In this work, wind farm layout optimization problem is dealt with a new approach. The aim of this work is maximizing the output power of a wind farm by considering wake loses. Layout optimization minimizes the wake loses regarding the wind direction. Three different wind scenarios including different wind direction angles, wind direction blowing probabilities and Weibull distribution parameters for wind speed are assumed. Since, the problem is nonlinear and constrained, imperialist competitive algorithm is used as a modern and powerful algorithm for continuous optimization problems. The optimization outcomes indicate that imperialist competitive algorithm yields promising results.... 

Use of wind energy is always one of the aims of man during the times. He used this energy for wheat grinding and sometimes for marine transportations. During recent decades, technology development forced human to harness this energy and use that for electricity production by employing onshore wind turbines. However, the modern engineering employed different arms of engineering such as marine engineering, civil engineering, mechanical engineering and electrical engineering for designing and installation of offshore wind turbines. But, huge water depths in offshore regions make the fixed leg turbines to be unacceptable solution. So, the floating wind turbines with mooring lines which attach... 

Nowadays, microgrids which comprise decentralized generation (DG) have attracted considerable attention. Establishment of DG-based microgrids that are normally connected to the main grid, is a practical method to reduce the costs of power outage and to increase the electricity supply reliability. The aim of this thesis is optimum planning of a microgrid containing wind turbines, photovoltaic systems and diesel generators, considering both the grid-connected and isolated modes of operation.
In the areas with considerable solar radiation and wind potential valuable opportunities exist in utilizing these resources. In addition to these renewable resources, the use of controllable resources... 

As a matter of fact, power systems are always faced with a variety of uncertainties. These uncertainties change system parameters in an unwanted manner which may deteriorate the system security and reliability. For instance, a transmission line which is designed for a certain capacity may be suffered as a result of load increment and consequently may influence the normal operation of other network elements. In recent years, as a result of environmental considerations and especially after the oil shock at 1973 which caused the the energy prices to increase unprecedentedly, the human has taken more attention to renewable energies exploitation. Theses energies have a fluctuating nature and are... 

The demand for electrical energy is increasing. The main source of energy at this moment is fossil fuels. High price, great amount of pollution, uneven distribution and global warming are major disadvantages of fossil fuels. Using renewable resources can tackle these issues. Hence, the demand for renewable energy are highly increased. The wind energy is one type of renewable energy. Increasing the wind power penetration impairs the functionality of power system and causes the environmental issues. In order to have a stable power system this effect should be investigated thoroughly. Due to the inherent uncertain characteristics of wind energy, it is desirable to determine the characteristics... 

According to the economic and environmental considerations, the use of distributed generation, both renewable and non-renewable type, in distribution networks is increasing. Their power generation is determined either by weather conditions or customers’ control due to their needs, therefore it is beyond the control of dispatcher.
In this thesis, two common technologies of distributed generations, including wind turbines and micro-CHPs, have been considered and the effects of their generations and penetrations on distribution network load and other network parameters have been evaluated.
Power generation of micro-CHP units and its side effects, is dependent on the customers’... 

Considerable attention has been given in recent years to renewable energy sources due to concerns about dwindling fuel reserves and the potential impact of conventional energy systems on the environment. Wind power is one form of renewable energy resources and also considered as Dispersed Generation (DG). Widespread utilization of wind power imposes many effects on planning and operation of power system. In other side, reliability evaluation and enhancement is an important factor in modern power system planning and operation. So, reliability assessment of wind turbines is of great importance and will receive more attention in the future according to increase of WT utilization. The... 

One of the special regimes of a wind turbine transformer operation is its repetitive connection and disconnection from the wind turbine (or the grid) via a short length of cable. Energizing the transformer will stress the transformer in two ways: the passage of inrush currents, and the initiation of possible high frequency resonances in the windings. In this thesis, first the 3D-wound core transformer design is investigated as a mean for reduction of the transformer inrush currents drawn from the grid. It is shown that this desirable performance is due to H-balance equation in this type of core and therefore the transformers of this type preserve a suitable response under energization to be... 

Global trends of electrical energy production indicate high penetration of renewable wind energy resources in power grids around the world.Although high penetration of these resources benefits the grid operators and end-users in various aspects, several new challenges should be addressed. These challenges can be focused on in various studies with different time intervals and different technical and economic issues. One of the most important issues relates to the system frequency regulation and control aspects in high wind and photovoltaic (PV) penetrated grids. This is due to the fact that wind turbine generators (WTGs) as well as PV systems do not provide inertial response for the system... 

Sustainable energy is an important and necessary subject. A significant number of studies address the increasing energy production ratio per its cost. To this end, first of all we should increase the energy production. Second, damage and costs of production, set up and maintenance must be reduced. Control is one of the most important and effective tools in the way of achieving these purposes. The problem of controlling a wind turbine is generally divided into two sections of controlling the power chain and yaw control. In this research, both subjects have been investigated.Since there are some problems in measuring the wind speed, controlling the power chain requires prediction of the wind... 

Through the last decades, due to environmental issues and to confine CO2 emission and also dependency to the fossil fuels, renewable energy resources has been developed. It’s been expected up to 2035, the renewable energy resources will be scaled three times and among those resources, the wind energy will stand prominently. Out of this king of renewable resource, the horizontal wind turbine has been subjected in this research.The focus of is to design the controller in third of a 2 MW turbine operation by which stable rotor speed and nominal output power to be attained. Besides, to enhance the accuracy of the windturbine profiles, the TURBSIM software (At the National Renewable Energy... 

This thesis aims at developing control system of a full converter wind turbine with modular and parallel back-to-back converters. Modular structures and paralleling of power electronic converters are the state-of-the-art methods for increasing their transferable power to the grid. Technological advances in high power wind turbines, especially for the offshore installations, which contain permanent magnet synchronous generators with back-to-back full converters, promote the use of modular structures.
In addition to developing the regular control systems of wind turbines for modular structures, selection of appropriate structures, power sharing between parallel converters and mitigation of... 

Nowadays, due to gearbox drawbacks, the direct-drive wind turbines have received much more attention. Permanent magnet synchronous machines are commonly used for this purpose. The flux reversal machine with a magnetic gearbox and high power density could be an appropriate alternative. Due to placement of permanent magnets on the stator, the machine has a simple and robust structure and provides more reliability. There is limited study on optimization of the flux reversal machine and the existing papers are not complete and many parameters like PM dimension, working temperature, and winding reactance are not considered in the optimization process.Considering the flux reversal machine... 

Fast improvements in the wind turbine technologies as well as the growing concern over sustainable power supply have led to the proliferation of wind energy. The upward trend in installed wind capacity is evident from the fact more than 120 GW of wind turbine capacity has been installed globally in 2018-2019, resulting in 591 GW of globally available wind capacity. The high penetration of renewable resources such as wind-turbine generators can cause inevitable changes in the dynamic behavior of power grids, especially in the frequency stability. Accordingly, it is imperative to perform comprehensive studies about the impacts of wind power on the power system frequency. Increasing wind...